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From: Jan K. <jan...@si...> - 2010-10-07 09:33:51
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Am 07.10.2010 11:27, Gilles Chanteperdrix wrote: > Jan Kiszka wrote: >> Am 07.10.2010 11:13, Gilles Chanteperdrix wrote: >>> Jan Kiszka wrote: >>>> Am 04.10.2010 22:13, Edward Hoffman wrote: >>>>> I am attempting to port the Broadcom tg3 NetXtreme linux driver to >>>>> rtnet. >>>> Your port will be welcome! >>>> >>>>> The Broadcom driver internally utilizes >>>>> spin_lock_bh/spin_unlock_bh to disable/enable software interrupts. >>>>> There is no rtdm lock equivalent. >>>>> I believe that software interrupts are used by the driver for the >>>>> following reasons: >>>>> 1. To allow for simultaneous DMA read write operations >>>>> 2. To use shared local variables in a critical section of the driver. >>>>> 3. To receive changes to settings variables in realtime from the >>>>> userpace Nextreme utilities. (not sure about this one). >>>>> >>>>> What RTDM lock functions should I use to substitute for >>>>> spin_lock_bh/spin_unlock_bh? Should I substitute >>>>> rtdm_lock_get_irqsave/rtdm_lock_put_irqrestore? Or does rtdm need to ne >>>>> extended for softirqs used internally by the driver? >>>>> >>>>> I looked through the other device drivers and could not detect the >>>>> correct substitute. >>>> As RTDM provides no abstraction of bottom-halves, there are also no >>>> specific locking services to disable them. You have to use IRQ-disabling >>>> services unless you are in IRQ context. >>> Maybe if you want to only exclude the driver's irq, you may only disable >>> the irq line at IC level, with rtdm_irq_disable? >> >> Usually discouraged due to potentially slow line-disabling services and >> the breakage this will cause when the line is shared. > > Why would this cause breakage when the line is shared? If the disabling context is preemptible (which is normally the motivation when avoiding irqsave), the line may remain off until that task happens to be scheduled in again. That can easily cause prio-inversions to other devices sharing the line. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux |
